My personal opinion (and it is really just that - I cannot prove anything I say here) is that for a lot of those companies it is actually the risk of not being able to tell exactly what the AGPL would affect that is the main factor.

As I said, I'm explicitly not mentioning any alternative here because they all have issues, but the AGPL's wording is much more complicated than most and that (perceived) insecurity around it is my main criticism.